1. Field of the Invention
The present invention relates to a gear pump for carrying high viscous fluid such as molten resins.
2. Description of the Related Art
For example, the gear pump for carrying molten resins has a pair of gear rotors, that being supported rotatably the pump body through a bearing. The bearing is a slide bearing, which is of a self-lubricating type in which a part of the molten resins to be carried as bearing lubricating agent.
In the gear pump of this kind, it is important to increase the production amount (carrying amount), and methods thereof include a method for increasing the number of revolutions and a method for widening the tooth width. However, in any of these methods, the burden on the bearing increases to lead to high possibility of baking, which makes difficult to increase the production amount.
That is, when the number of revolutions is increased, the shearing speed is high, which results in high heat generation of resins and lowering bearing support ability. Further, when the tooth width is widened, the load increases, and the bearing support ability lowers.
In view of the above, in the gear pump of this kind, it is most effective for enhancing the bearing ability to lower a temperature of the molten resins as lubricant to raise the viscosity of resins.
Methods for cooling the lubricant (molten resins) include a method for cooling a rotor shaft (for example, see U.S. Pat. No. 5,292,237), a method for cooling a bearing (for example, see U.S. Pat. No. 5,924,854), or a method for cooling a bearing (for example, see Japanese Patent Application Laid-Open No. Hei 10-141247 Publication).
In the aforementioned U.S. Pat. No. 5,924,854, a bearing and a viscous seal are integrated to thereby prevent leakage of a temperature adjusting medium and that of resins.
However, this poses a problem that because of the construction in which the bearing is secured to the body, an unreasonable load is applied to the bearing.
That is, since the bearing is pressed in a different direction depending on the operating conditions such as the discharge pressure or the number of revolutions, it is preferable that the bearing be mounted in the free state with respect to the body. However, when it is secured to the body as in the prior art described previously, there occurs a problem that the unreasonable load is applied to the bearing.
Especially, in case of an arrangement in which a bearing is cooled, a clearance present between the bearing and the body is further enlarged by cooling the bearing, which makes the problem further serious.
The aforementioned integral type has a problem that manufacturing is difficult and the cost increases.
On the other hand, in the disclosure of Japanese Patent Application Laid-Open No. Hei 10-141247 Publication, the bearing is constituted separately from the viscous seal, but there is a problem that the cooling medium leaks or assembling is difficult.
That is, an inlet passage or an outlet passage of cooling medium with respect to the bearing are provided on a cover (side plate) for securing the bearing, and a seal construction between the cover and the bearing is difficult.
It is therefore an object of the present invention to provide a gear pump for carrying high viscous liquid, which keeps a bearing free, and enhances reliability relative to leakage of cooling medium or leakage of molten resins.
For achieving the aforementioned object, the present invention employs the following constitutions.
According to the present invention, there is provided a gear pump comprising: a body; a bearing; a pair of gear rotors, said gear rotors being supported on said body through said bearing; a cover for preventing said bearing from being slipped out in the axial direction of said bearing, said cover being secured to said body; a temperature adjusting medium passage formed in said bearing; an inlet pipe provided on the axial outer end of said bearing, said inlet pipe being communicated with said temperature adjusting medium passage; an outlet pipe provided on the axial outer end of said bearing, said outlet pipe being communicated with said temperature adjusting medium passage; and an intermediate plate interposed between the axial outer end of said bearing and said cover, said intermediate plate being formed with a hole for inserting said input pipe and said outlet pipe therein, wherein said cover is provided with a guide portion having said inlet pipe and said outlet pipe loosely fitted therein to guide them to outside.
The provision of the intermediate plate, as described above, enables positive prevention of the leakage of temperature adjusting medium and the leakage of material to be carried. In addition, in place of inserting the inlet pipe and the outlet pipe into the cover, constitution of inserting them into the intermediate plate may be employed to thereby facilitate assembling.
In the gear pump according to the present invention, preferably, said bearing is held on said body in a non-secured state. By such a constitution as described, unreasonable load is not applied to the bearing.
In the gear pump according to the present invention, preferably, the pump is for carrying molten resins.
In the gear pump according to the present invention, preferably, constitution is employed in which a part of the carried material to be supplied as lubricant between said bearing and said gear rotor.
In the gear pump according to the present invention, constitution is employed in which said guide portion is depressed along the diametrical direction of said rotor on the intermediate plate side end of said cover.
In the gear pump according to the present invention, both end surfaces of said intermediate plate may comprise seal surfaces.
In the gear pump according to the present invention, both end surfaces of said intermediate plate may contact with said bearing and said cover through a seal member.
In the gear pump according to the present invention, said inlet pipe and said outlet pipe may be mounted on said bearing through watertight means.
In the gear pump according to the present invention, said intermediate plate may be integrated with a thrust plate provided in order to locate said bearing in an axial direction. Said thrust plate is provided separately from said bearing.
Further, in the gear pump according to the present invention, there are provided a viscous seal for preventing leakage of liquid form said gear rotor, said viscous seal being provided at an axial outer position of said bearing, and fastening means provided on said viscous seal, said fastening means raising mounting surface pressure of said intermediate plate and said cover.
Further, according to the present invention, there is provided a gear pump comprising: a body; a bearing; a pair of gear rotors, said gear rotors being supported on said body through said bearing; a cover for preventing said bearing from being slipped out in the axial direction of the bearing, said cover being secured to said body; temperature adjusting medium passage formed in said bearing; an inlet pipe provided on the axial outer end of said bearing, said inlet pipe being communicated with said temperature adjusting medium passage, at least a part of said inlet pipe being formed from a flexible member; and an outlet pipe provided on the axial outer end of said bearing, said outlet pipe being communicated with said temperature adjusting medium passage, at least a part of said outlet pipe being formed from a flexible member, wherein said cover is provided with a guide portion having said inlet pipe and said outlet pipe loosely fitted therein to guide them to outside.
By being constituted as described above, it is possible to realize a gear pump capable of preventing leakage of temperature adjusting medium and leakage of material to be carried positively, and facilitating assembling.
Further, in the gear pump according to the present invention, constitution can be employed in which the guide portion is provided in parallel with the shaft center of the gear rotor, and the diameter of the guide portion is larger than that of the inlet pipe and larger than that of the outlet pipe.